You must be having 'Show HTTP friendly errors' turned on in the browser. Please disable it and see what message IIS is giving. For IE, you can go to Tools->Internet Options, then go to Advanced tab and uncheck 'Show HTTP friendly error' check box.
Since you are still using localhost and default port 80 (I am guessing that looking at your URL), I am assuming that you changed the physical path of your default web site to something else using 'inetmgr'. I hope IIS has got permission to run the content.
Please turn off browser friendly error and let us know what are you seeing in the detailed error page?
Thanks,
Don.